Abstract: A structure scheme of shim-rod assembly including absorber bundle, gripper, ballast, inner wrapper, wrapper etc. was proposed to solve the problem caused by the high density and high buoyancy coolant in the lead-bismuth cooled reactor. The mechanical analysis of the inner wrapper and the upper gripper was carried out based on the computation performed by finite element method. The stress changing tendency of the inner wrapper was analyzed and the structure of the upper gripper was verified, which indicates the feasibility of the shim-rod assembly design, providing a reference for other internals facing similar environments in LBE cooled reactors.

Key words: lead-bismuth cooled reactor, shim-rod, assembly